Thousands of firefighters, railroad workers, bus drivers, truck drivers, mechanics, construction and tunnel workers, coal and metal/non-metal miners, and other workers are exposed to diesel engine exhaust. Diesel engine exhaust contains particulate matter and toxic gases such as formaldehyde, nitrogen dioxide, and carbon monoxide. Diesel exhaust particulate (DEP) consists of a black carbon core and adsorbed surface compounds like polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs. Diesel exhaust has been classified as a suspected human carcinogen and exposure has been linked to lung and other cancers. The specific aim of this project is to reduce the risk of lung cancer and other cancers in workers by developing and testing practical technology to control DEP emissions from workplace machinery. Electrostatic precipitators (ESPs) have been used for nearly a century to control air emissions from power plants and industrial facilities. ESP technology has not been successfully miniaturized to control emissions from diesel-powered machinery. The state-of-the-art technology presently available for diesel exhaust after treatment, the mechanical filter, is unlikely to be effective on many workplace diesels. This project is directly related to NORA priority area of "Control Technology and Personal Protective Equipment" and has four specific objectives: (1) Construct an electrical test cell to investigate and establish the voltage/current properties of miniature electrostatic precipitators, (2) Build a facility for investigating small diesel engine emissions, (3) Construct and test a miniature electrostatic precipitator (the mini-ESP) to control particulate emissions from a diesel electric generator, (4) Use the test results to develop and publish a model for the design of future diesel particulate electrostatic precipitators.